Vertical Lapse Rate Research Articles

How is the relationship between rainfall and water vapor in the Indian monsoon influenced by changes in lapse rate during global warming?

Most climate models have shown that the Indian Summer Monsoon Rainfall (ISMR) will increase on account of global warming. The primary reason is the increase in column water vapor (CWV). The rainfall increase is not, however, proportional to the increase in column water vapor; for a given amount of CWV, rainfall will be lower in the future, according to model simulations. This suggests that other there are factors are at play. We have used a diagnostic model based on moist static energy (MSE) and moisture conservation to examine the impact of changes in the vertical lapse rate of temperature. Our results indicate that on decadal time scales, changes in ISMR are mediated by changes in CWV and temperature lapse rates. This is consistent with previous studies that showed the impact of column-mean temperature on the rainfall-CWV relationship. Findings are significant for climate model projections of ISMR, as correct estimation of lapse rate changes in models is necessary to predict ISMR changes accurately.

Micrometeorological Analysis and Glacier Ablation Simulation in East Kunlun

Worldwide, there are great challenges for meteorological monitoring and glacier ablation monitoring in high-altitude mountain areas. It is often difficult to capture fine-scale climate and glacial changes in high-altitude mountainous areas due to the harsh natural environment and the extreme lack of observational sites. Based on high-altitude meteorological stations erected on the eastern shore of Aqikkule Lake (AQK) and at the terminus of Shenshechuan Glacier (SSG), as well as on mass balance data from SSG, the characteristics and correlation of temperature, solar radiation, relative humidity, precipitation, wind speed and direction of the two regions, and the mass balance in the ablation area of SSG from 30 May 2022 to 18 May 2023 were analyzed, and the average melting depth of SSG was simulated. The results indicate the following: (1) The average annual temperature of AQK and the terminus of SSG is −3.7 °C and −7.7 °C, respectively, and the vertical lapse rate of temperature in the summer half of the year is greater than that in the winter half of the year. Precipitation timing has a great influence on daily temperature differences. (2) Precipitation in both places is concentrated in summer; the glaciers in this area are of the summer recharge type, and precipitation has a significant reducing effect on the solar incident radiation and increases the relative humidity in this region. (3) AQK and SSG both have local circulation development, in the area of AQK all year round due to the lake effect, while the terminus of SSG only has the development of valley winds in the summer, being controlled in the winter by the westerly wind belt. (4) The average mass balance value of the ablation area of SSG was −1786 mm as measured by the range poles method. The average annual ablation depth of SSG simulated by using the empirical formula was 587–597 mm, which is not large compared with other glacier areas in the Tibetan Plateau, and it has the characteristics of typical continental-type glaciers.

Why Is Climate Sensitivity for Solar Forcing Smaller than for an Equivalent CO2 Forcing?

Abstract Previous studies have shown that climate sensitivity, defined as the global mean surface temperature change per unit radiative forcing, is smaller for solar radiative forcing compared to an equivalent CO2 radiative forcing. We investigate the causes for this difference using the NCAR CAM4 model. The contributions to the climate feedback parameter, which is inversely related to climate sensitivity, are estimated for water vapor, lapse rate, Planck, albedo, and cloud feedbacks using the radiative kernel technique. The total feedback estimated for CO2 and solar radiative forcing from our model simulations is −1.23 and −1.45 W m−2 K−1, respectively. We find that the difference in feedback between the two cases is primarily due to differences in lapse rate, water vapor, and cloud feedbacks, which together explain 65% of the difference in total feedback. The rest comes from Planck and albedo feedbacks. The differences in feedbacks arise mainly from differences in the horizontal (meridional) structure of forcing and the consequent warming. Our study provides important insights into the effects of the meridional structure of forcing on climate feedback, which is important for evaluating global climate change from different forcing agents. Significance Statement An increase in atmospheric CO2 concentration or an increase in incoming solar radiation leads to a rise in the radiative budget and consequent climate warming, which is amplified by the presence of multiple climate feedbacks. These feedbacks, from changes in surface albedo, combined effect of water vapor and the vertical lapse rate of temperature, and changes in clouds, differ between solar and CO2 forcing. Using radiative kernels, this study quantifies these individual feedbacks for an equivalent radiative change caused by an increase in CO2 or incoming solar radiation, showing how the differences arise from differences in the meridional patterns of warming. In agreement with prior studies, these differences can explain the smaller efficacy of solar forcing compared to CO2 forcing.

Bias correction of ERA-Interim reanalysis temperature for the Qilian Mountains of China

Air temperature is the primary indicator of climate change. Reanalysis temperature products are important datasets for temperature estimates over high-elevation areas with few meteorological stations. However, they contain biases in observations, so a bias correction is required to enhance the accuracy of modeling predictions. In this study, we used the temperature lapse-rate method to correct ERA-Interim reanalysis-temperature data in the Qilian Mountains of China from 1979 to 2017. These temperature lapse rates were based on observations (ΓObs) and on model internal vertical lapse rates derived from different ERA-Interim pressure levels (ΓERA). The results showed that the temperature lapse rates in warm periods were larger than those in cold periods. Both the original and corrected ERA-Interim temperature can significantly capture the warming trend exhibited by observations. In general, the temperature lapse rate method was reliable for correcting ERA-interim reanalysis-temperature data. Although ΓObs performed best in bias correction, it depends heavily on the density of ground observation stations and is not appropriate for remote areas with a low data coverage. Correction methods based on ΓERA were shown to be reliable for bias correction, and will be especially applicable to mountainous areas with few observation stations. Our results contribute to the improvement of quality of data products and enhance the accuracy of modeling of climate change effects and risks to the environment and human health.

Spatial variations of hydrochemistry and stable isotopes in mountainous river water from the Central Asian headwaters of the Tajikistan Pamirs

Water resources in Central Asia from the mountainous headwater catchments is changing due to the shrinkage of glaciers in the Tian Shan and Pamir mountain systems. In order to predict future changes in water quality, it is crucial to understand what factors are governing the spatial variations of water chemistry and hydrological processes in mountainous headwater catchments. In this study, water chemistry including major ions and stable isotopes in the headwaters of major Tajikistan rivers was studied. Results showed that Tajikistan river water had an alkaline pH value (mean: 8.2) and total dissolved solids (mean: 368.5mg/L) were higher than the global average value. Ca2+, Na+, HCO3−, and SO42− in the rivers were the most abundant cations and anions, controlled by the rock weathering process and evaporation-crystallization processes. The hydrochemical facies of river water was dominated by Ca-HCO3 (71.7%) and exhibited spatial heterogeneity, which was related to the lithologic compositions and water source across Tajikistan. A significant negative correlation of river water δ18O with elevation was observed with a vertical lapse rate of 0.17‰/100 m. The more negative δ18O values in rivers from eastern Tajikistan were scattered in the lower left corner of the δ18O-δ2H plot, implying that the rivers were primarily supplied by snow/glacier meltwater because of the substantial number of glaciers and high elevation mountain in eastern regions. The drinking and irrigation suitability from ionic compositions revealed that the water quality of Tajikistan rivers was naturally good, though some sites posed a safety concern. These findings can provide new insights into sustainable management of water quality in the climatically and lithologically distinct segments of headwater regions in the Tajikistan Pamirs.

Spatial and temporal variability of stable isotopes (δ18O and δ2H) in surface waters of arid, mountainous Central Asia

AbstractCharacterization of spatial and temporal variability of stable isotopes (δ18O and δ2H) of surface waters is essential to interpret hydrological processes and establish modern isotope–elevation gradients across mountainous terrains. Here, we present stable isotope data for river waters across Kyrgyzstan. River water isotopes exhibit substantial spatial heterogeneity among different watersheds in Kyrgyzstan. Higher river water isotope values were found mainly in the Issyk‐Kul Lake watershed, whereas waters in the Son‐Kul Lake watershed display lower values. Results show a close δ18O–δ2H relation between river water and the local meteoric water line, implying that river water experiences little evaporative enrichment. River water from the high‐elevation regions (e.g., Naryn and Son‐Kul Lake watershed) had the most negative isotope values, implying that river water is dominated by snowmelt. Higher deuterium excess (average d = 13.9‰) in river water probably represents the isotopic signature of combined contributions from direct precipitation and glacier melt in stream discharge across Kyrgyzstan. A significant relationship between river water δ18O and elevation was observed with a vertical lapse rate of 0.13‰/100 m. These findings provide crucial information about hydrological processes across Kyrgyzstan and contribute to a better understanding of the paleoclimate/elevation reconstruction of this region.

Application of Multivariate Sensitivity Analysis Techniques to AGCM-Simulated Tropical Cyclones

Abstract This work demonstrates the use of Sobol’s sensitivity analysis framework to examine multivariate input–output relationships in dynamical systems. The methodology allows simultaneous exploration of the effect of changes in multiple inputs, and accommodates nonlinear interaction effects among parameters in a computationally affordable way. The concept is illustrated via computation of the sensitivities of atmospheric general circulation model (AGCM)-simulated tropical cyclones to changes in model initial conditions. Specifically, Sobol’s variance-based sensitivity analysis is used to examine the response of cyclone intensity, cloud radiative forcing, cloud content, and precipitation rate to changes in initial conditions in an idealized AGCM-simulated tropical cyclone (TC). Control factors of interest include the following: initial vortex size and intensity, environmental sea surface temperature, vertical lapse rate, and midlevel relative humidity. The sensitivity analysis demonstrates systematic increases in TC intensity with increasing sea surface temperature and atmospheric temperature lapse rates, consistent with many previous studies. However, there are nonlinear interactions among control factors that affect the response of the precipitation rate, cloud content, and radiative forcing. In addition, sensitivities to control factors differ significantly when the model is run at different resolution, and coarse-resolution simulations are unable to produce a realistic TC. The results demonstrate the effectiveness of a quantitative sensitivity analysis framework for the exploration of dynamic system responses to perturbations, and have implications for the generation of ensembles.

Controls on the stable isotopes in precipitation and surface waters across the southeastern Tibetan Plateau

Constraining temporal and spatial variability in water stable isotopes (δ18O and δD) is requested for interpreting proxy records of paleoclimate/paleoaltimetry. The southeastern Tibetan Plateau (TP) receives large amounts of precipitation in both summer (JJAS) and spring (MAM) and this makes it different from most other parts of the TP where annual precipitation concentrates only in summer. However, our knowledge of controls on precipitation and surface runoff generation in this region is still far from sufficient. In this study, the δ18O and δD of precipitation and stream waters across the southeastern TP were analyzed to investigate moisture sources and empirical isotope-elevation relationships. Herein, seasonal precipitation patterns, moisture trajectories and precipitation isotopes suggest this region is seasonally dominated by the monsoon in summer and the southerlies (from the Bay of Bengal) or a mix of southerlies and westerlies in spring. Spatially, vertical variations in precipitation seasonality exert profound influences on isotopic variability for stream waters. Larger contributions of spring precipitation (with higher δ18O and d-excess (d-excess=δD-8δ18O) compared to summer precipitation) vs. summer precipitation in the surface runoff generation at lower elevations account for the uncommon altitudinal decrease in streamwater d-excess. Such a cause also contributes to the slightly greater vertical lapse rates of streamwater δ18O (−0.28 to −0.48‰/100m) relative to the Himalayan front. In addition, although a robust δ18O-elevation relationship is demonstrated based upon our measured and other published data on a broad spatial scale (over a 5200m elevation range), this relationship is found to deviate from the empirical/theoretical pattern in the Himalayan front, which is also caused by the substantial spring precipitation in the southeastern TP. It is suggested that long-term changes in δ18O or δD of paleowater in this region actually represent both changes in past regional elevations and contributions of summer vs. spring atmospheric circulations.

Elevation correction of ERA‐Interim temperature data in the Tibetan Plateau

ABSTRACTThe near surface air temperature is the primary indicator for climate change. Reanalysis as the surrogates for large‐scale observations are widely used in the Tibetan Plateau because of the sparse meteorological network. However, an average bias of −3.54 °C and root‐mean‐square error (RMSE) of 4.31 °C were found between ERA‐Interim monthly 2‐m temperature and observation over the Tibetan Plateau, which indicated that a correction procedure for ERA‐Interim is necessary before local scale applications. To overcome this challenge, a robust elevation correction method is developed to downscale ERA‐Interim 2° × 2° monthly 2‐m temperature data based on ERA‐Interim internal vertical lapse rates. This method is validated against 80 meteorological stations from 1979 to 2013 located in 26 ERA‐Interim grid cells. It is also compared with other four correction methods, which are using different lapse rate schemes such as fixed monthly lapse rates, surface lapse rates calculated from the meteorological stations (within a single grid or with neighbouring sites), as well as a third‐order curvilinear function of ERA‐Interim pressure level data. The results indicate that the correction method using ERA‐Interim internal vertical lapse rates cannot only significantly reduce the bias (89%) and RMSE (62%) for the original ERA‐Interim data, but also capture the inter‐annual variations for the plateau‐wide climatology very well. The seasonal and annual temperature warming trends are also modelled encouragingly compared with other four methods. The strongest advantage of this method is that it is independent of local meteorological stations. Therefore, it is possible to extrapolate ERA‐Interim temperature data for any other high mountain areas where no measurements exist. This work will help the scientific community identify the most proper and easiest method to downscale reanalysis temperature data for climate impact assessments at the site or regional scale.

An isolated tornadic supercell of 14 July 2012 in Poland — A prediction technique within the use of coarse-grid WRF simulation

On 14 July 2012 a shortwave trough with a cold front passed through Poland. A few tornadoes were reported in the north central part of the country within an isolated cyclic supercell. The cell moved along the thermal and moisture horizontal gradients and the support of a synoptic scale lift. An analysis allowed for setting up four tornado damage tracks in a distance of 100km and with a total length of 60km. Tornadoes damaged 105 buildings with predominant intensity of F1-F2/T3-T4 (maximum F3/T6) in Fujita/TORRO scale, caused 1 fatality, 10 injures and felled 500 hectares of Bory Tucholskie forest. The main aim of this article was to analyze this event and assess the possibilities of its short-term prediction. In order to achieve this, a model forecast data derived from WRF-ARW simulation with a spatial resolution of 15km and initial conditions extracted from 0000 UTC GFS was used. An analysis yielded that the cell moved in the environment of a low lifting condensation level, rich boundary layer's moisture content and a steepening vertical lapse rates that provided the presence of a thermodynamic instability. A wind vectors tilting with height and an increased vertical wind shear occurred as well. A forecasting method that combined a Universal Tornadic Index composite parameter with a convective precipitation filter showed that convective cells at 1500 UTC in the north central Poland had a potential to become tornadic. Within the use of a proposed methodology, it was possible to issue a tornado forecast for the areas where an index pointed the risk.

Energetics and monsoon bifurcations

Monsoons involve increases in dry static energy (DSE), with primary contributions from increased shortwave radiation and condensation of water vapor, compensated by DSE export via horizontal fluxes in monsoonal circulations. We introduce a simple box-model characterizing evolution of the DSE budget to study nonlinear dynamics of steady-state monsoons. Horizontal fluxes of DSE are stabilizing during monsoons, exporting DSE and hence weakening the monsoonal circulation. By contrast latent heat addition (LHA) due to condensation of water vapor destabilizes, by increasing the DSE budget. These two factors, horizontal DSE fluxes and LHA, are most strongly dependent on the contrast in tropospheric mean temperature between land and ocean. For the steady-state DSE in the box-model to be stable, the DSE flux should depend more strongly on the temperature contrast than LHA; stronger circulation then reduces DSE and thereby restores equilibrium. We present conditions for this to occur. The main focus of the paper is describing conditions for bifurcation behavior of simple models. Previous authors presented a minimal model of abrupt monsoon transitions and argued that such behavior can be related to a positive feedback called the ‘moisture advection feedback’. However, by accounting for the effect of vertical lapse rate of temperature on the DSE flux, we show that bifurcations are not a generic property of such models despite these fluxes being nonlinear in the temperature contrast. We explain the origin of this behavior and describe conditions for a bifurcation to occur. This is illustrated for the case of the July-mean monsoon over India. The default model with mean parameter estimates does not contain a bifurcation, but the model admits bifurcation as parameters are varied.

Application of a distributed degree-day model of glaciers in the upper reaches of the Beida River Basin

Based on in-situ data of Qiyi Glacier from 2010 to 2012, a daily distributed degree-day model on a 90 × 90 m grid was developed to simulate the spatial and temporal variations of the glacier mass balance, ELA, and meltwater run-off depth in the Beida River Basin from 1957 to 2012. In the model, different vertical lapse rates of temperature and precipitation gradients were used in different months and height-belts, and the influence of ‘temperature jump’ was also considered. The results indicated that the average annual mass balance and meltwater run-off depth of the glaciers in the Beida River Basin were −93.3 mm w. e. and 443 mm, respectively. Assuming a continuous linear trend, the ELA had risen by 505 m over 55 years. The mass balance linearly increased with the altitude in the cold season (Oct.–Apr.) and exponentially in the warm season (May–Sep.). The most possible abrupt change points of the mass balance, ELA, and meltwater run-off depth time series were all in 1992/93, as determined through the M–K test. The mass balance turned increasingly negative since then, but the ELA and meltwater run-off increased rapidly. The climate sensitivity test showed that the air temperature was a dominant factor that affected the mass balance of the continental glaciers on the basin scale, which was different from the response mechanism of maritime glaciers. When the air temperature (+1 °C) and precipitation (+10 %) increased simultaneously, the glacier mass loss and meltwater run-off reached 1.66 × 108 m3 and 2.45 × 108 m3, respectively.

Atmospheric conditions of thunderstorms in the European part of the Arctic derived from sounding and reanalysis data

While thunderstorms in equatorial and mid-latitudes are well documented, little is known about their presence in high latitudes. There are barely a few studies on this phenomenon analyzing their occurrence in the European Arctic region. In an attempt to rectify this situation authors aim to explain which conditions are conducive to their formation in Bjørnøya, Jan Mayen and Svalbard islands. A total of 41 thunderstorm days derived from SYNOP reports from the period of 1981–2010 were used to define thunderstorm-favorable synoptic conditions from NCEP/NCAR reanalyses and sounding data. In order to underline seasonal variation, anomalies were presented in the polar day and polar night timeframes. As it turned out polar night thunderstorms occur most often in situations with southern warm marine air advections intensified by the positive North Atlantic and Arctic Oscillations. Thunderstorms in this season are characterized by steep vertical lapse rates and occur most likely at the cold fronts. Polar day thunderstorms form when warm air masses move from the continental north-eastern Europe to the Arctic, and create unstable conditions. In this type, thunderstorms are generated by elevated convection and occur most likely in a cyclone's cool side of warm sector.

A study of longitudinal and altitudinal variations in surface water stable isotopes in West Pamir, Tajikistan

In an effort to establish a clear relation between stable isotopes and altitude in the Pamir region, as well as to improve the understanding of stable isotope spatial variations found along the routes taken by the westerlies, surface river water samples were collected along a roughly west–east profile in Tajikistan. Here we present the spatial changes in modern surface water δ18O and deuterium excess (d-excess), and their links with snow melt, glacier melt and seasonal precipitation patterns in Tajikistan. The results show a close relation between river water δ18O and δD above the GMWL (Global Meteoric Water Line), implying that surface evaporation exerts a weaker influence. Spatially, river water δ18O is gradually depleted from west to east due mainly to the effect of altitude, yielding a river water δ18O vertical lapse rate of 0.09‰/100m. River water d-excess shows a decreasing trend from west to east in Tajikistan. This spatial d-excess pattern in surface water is explained by the different moistures influenced by the Mediterranean and other in-land seas with higher d-excess in west, and no-Mediterranean moisture in east. Another possible reason is the differences in precipitation seasonality between the west and east of Tajikistan.

Assessment of radiative feedback in climate models using satellite observations of annual flux variation

In the climate system, two types of radiative feedback are in operation. The feedback of the first kind involves the radiative damping of the vertically uniform temperature perturbation of the troposphere and Earth's surface that approximately follows the Stefan-Boltzmann law of blackbody radiation. The second kind involves the change in the vertical lapse rate of temperature, water vapor, and clouds in the troposphere and albedo of the Earth's surface. Using satellite observations of the annual variation of the outgoing flux of longwave radiation and that of reflected solar radiation at the top of the atmosphere, this study estimates the so-called "gain factor," which characterizes the strength of radiative feedback of the second kind that operates on the annually varying, global-scale perturbation of temperature at the Earth's surface. The gain factor is computed not only for all sky but also for clear sky. The gain factor of so-called "cloud radiative forcing" is then computed as the difference between the two. The gain factors thus obtained are compared with those obtained from 35 models that were used for the fourth and fifth Intergovernmental Panel on Climate Change assessment. Here, we show that the gain factors obtained from satellite observations of cloud radiative forcing are effective for identifying systematic biases of the feedback processes that control the sensitivity of simulated climate, providing useful information for validating and improving a climate model.

Elevation correction of ERA-Interim temperature data in complex terrain

Abstract. Air temperature controls a large variety of environmental processes, and is an essential input parameter for land surface models, for example in hydrology, ecology and climatology. However, meteorological networks, which can provide the necessary information, are commonly sparse in complex terrains, especially in high mountainous regions. In order to provide temperature data in an adequate temporal and spatial resolution for local scale applications a new elevation correction method has been developed that is able to downscale 3-hourly ERA-Interim temperature data. The scheme is based on model internal vertical lapse rates derived from different ERA-Interim pressure levels and has been validated for twelve meteorological stations in the German and Swiss Alps. The method was also compared with two other statistical, lapse rate based correction approaches. The results indicate that the use of model internal ERA-Interim lapse rates can significantly improve the downscaling performance when compared to the standard procedure of using fixed lapse rates.

CALIPSO observations of transatlantic dust: vertical stratification and effect of clouds

Abstract. We use CALIOP nighttime measurements of lidar backscatter, color and depolarization ratios, as well as particulate retrievals during the summer of 2007 to study transatlantic dust properties downwind of Saharan sources, and to examine the influence of nearby clouds on dust. Our analysis suggests that (1) under clear skies, while lidar backscatter and color ratio do not change much with altitude and longitude in the Saharan Air Layer (SAL), depolarization ratio increases with altitude and decreases westward in the SAL; (2) the vertical lapse rate of dust depolarization ratio, introduced here, increases within SAL as plumes move westward; (3) nearby clouds barely affect the backscatter and color ratio of dust volumes within SAL but not so below SAL. Moreover, the presence of nearby clouds tends to decrease the depolarization of dust volumes within SAL. Finally, (4) the odds of CALIOP finding dust below SAL next to clouds are about ⅔ of those far away from clouds. This feature, together with an apparent increase in depolarization ratio near clouds, indicates that particles in some dust volumes loose asphericity in the humid air near clouds, and cannot be identified by CALIPSO as dust.

Simulation of the Decadal Permafrost Distribution on the Qinghai‐Tibet Plateau (China) over the Past 50 Years

ABSTRACTDecadal changes in permafrost distribution on the Qinghai‐Tibet Plateau (QTP) over the past 50 years (1960–2009) were simulated with a response model that uses data from a digital elevation model, mean annual air temperature (MAAT) and the vertical lapse rate of temperature. Compared with published maps of permafrost distribution, the accuracy of the simulated results is about 85 per cent. The simulation results show: (1) with the continuously rising MAAT over the past 50 years, the simulated areas of permafrost on the QTP have continuously decreased; (2) through areal statistics, the simulated areas of permafrost were 1.60 × 106 km2, 1.49 × 106 km2, 1.45 × 106 km2, 1.36 × 106 km2 and 1.27 × 106 km2, respectively, in the 1960s, 1970s, 1980s, 1990s and 2000s; and (3) the rate of permafrost loss has accelerated since the 1980s, and the total area of degraded permafrost is about 3.3 × 105 km2, which accounts for about one‐fifth of the total area of permafrost in the 1960s. Copyright © 2012 John Wiley & Sons, Ltd.

A new high resolution absolute temperature grid for the Greater Alpine Region back to 1780

ABSTRACTThis study presents a new gridded dataset providing absolute monthly mean temperatures across the Greater Alpine Region (GAR) of Europe at a spatial resolution of 5 arcmin (6 × 9 km in the region) from 1780 to 2008. The starting point was a set of long‐term homogenized station time series. To assure the quality of the analyses back in time, when the station density decreases, missing measurements were reconstructed by an Empirical Orthogonal Function analysis that can deal with gappy data. It is shown that the reconstructed values comprise similar statistical features to the observations and that the method produces no breaks between the reconstructions and the observations. The compound anomaly dataset was then interpolated separately for two different altitude ranges to preserve anomaly gradients between high and low elevations. This allowed for the derivation of individual anomalies at each grid point in GAR. Finally, these smooth anomalies were blended with the highly resolved monthly mean absolute temperature fields, provided by a project of the European Climate Support Network. The added value of this new high resolution and long‐term temperature dataset is shown and discussed using the examples of the height of the 0 °C altitude and vertical lapse rates. For the first time, these and other features are now available for more than two centuries in a topographically complex region like GAR.

On the relationship between cloud–radiation interaction, atmospheric stability and Atlantic tropical cyclones in a variable-resolution climate model

We compare two 28-year simulations performed with two versions of the Global Environmental Multiscale model run in variable-resolution mode. The two versions differ only by small differences in their radiation scheme. The most significant modification introduced is a reduction in the ice effective radius, which is observed to increase absorption of upwelling infrared radiation and increase temperature in the upper troposphere. The resulting change in vertical lapse rate is then observed to drive a resolution-dependent response of convection, which in turn modifies the zonal circulation and induces significant changes in simulated Atlantic tropical cyclone activity. The resulting change in vertical lapse rate and its implication in the context of anthropogenic climate change are discussed.